AM2 Memory Performance

The move by AMD from the current Socket 939 to Socket AM2 is pretty straightforward. We know the new AM2 processors will continue to be built using the same 90nm manufacturing process currently used for Athlon 64 processors; AMD does not show roadmaps with AM2 processors built on 65nm until early 2007. To this point AMD has also reiterated that AM2 will not bring any changes to the Athlon 64 core. In other words, the socket will change to the new AM2 Socket 940, but under the hood the current 939 and the upcoming AM2 940 will beat with the same heart. The only substantive difference expected with AM2 is the move from DDR memory to official AMD DDR2 Memory support.

With that in mind it is time to delve more deeply into the what is really new in AM2 - support for DDR2 memory with AMD's unique on-processor memory controller. Many have expressed expectations of remarkable performance increases for DDR2 on AM2. This would be at odds with what we have seen from DDR2 in the past. With the move of Intel's NetBurst architecture to DDR2 there were really no gains at all in memory performance. Those expecting big gains point out that the AM2 on-chip memory controller, like the Athlon 64 on-chip DDR controller, should provide much lower latency and higher efficiency than Intel's chipset-based memory controller for DDR2.

This is our first opportunity to look more closely at an AM2 DDR2 controller that might answer these questions about memory performance, since it is the first AM2 design to outperform Socket 939. Earlier AM2 spins could not match 939 memory performance, but they continued to improve. This is remarkable when you consider that new Intel processors pretty much have performed like final shipping processors some 5 months ahead of launch. AMD, on the other hand, has done most of their development work on the DDR2 memory controller in the last 3 months with just 6 weeks remaining before launch.

The most recent AM2 roadmap is still showing AM2 launching June 6, 2006 at Computex in Taipei. With just 6 weeks to go before launch, there is not a lot of time for surprises with AM2. As pointed out in AMD Socket-AM2 Performance Preview, there is not much wiggle room when OEMs expect mid-May shipments of AM2. All of this leads us to believe that our fourth spin of AM2 this year is very close to what will actually be shipping on June 6th. We can always hope for surprises, but given what AMD has said so far we should be very close to final silicon.

You already know that the AM2 does modestly outperform Athlon64 Socket 939. What will be explored here is how the memory controllers compare in latency and bandwidth, memory performance at various DDR2 settings compared to fast DDR400 2-2-2 memory, and basic overclocking performance of AM2 compared to Socket 939 when the CPU and memory are both pushed to improve performance.

Memory Test Configuration
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  • peternelson - Saturday, April 15, 2006 - link

    No I don't work for VIA or Transmeta but I do work in the IT Industry ;-)

    Efficeon chips were used in Orion Multisystems DT-12 and DS-96 cluster in a box computers and some notebooks.

    Whilst they have low power, they do lack performance for some applications compared to the latest chips. But using VLIW based code-morphing they do indeed run x86 code.

    Just call it a "good idea" rather than "unique" ;-)
    Reply
  • Bladen - Friday, April 14, 2006 - link

    Although DDR2 667 at 3-3-3 doesn't seem that common, all I can find is DDR2 667 4-4-4 or 5-5-5. Here in Australia anyway.

    Maybe when AM2 is released a rehash article featuring the higher latencies is in order.
    Reply
  • Gary Key - Saturday, April 15, 2006 - link

    quote:

    Although DDR2 667 at 3-3-3 doesn't seem that common, all I can find is DDR2 667 4-4-4 or 5-5-5. Here in Australia anyway.


    In our recent experiences with Infineon based DDR2-667 modules rated at 4-4-4, the majority of these modules will run at DDR2-667 with 3-3-3 settings with a voltage setting around 2.2V. Your mileage will vary based upon supplier but going with one of the more performance oriented providers will usually result in the better timings.

    We fully expect a wave of higher performance DDR2 modules to be launched in conjunction with the AM2 product. The majority of these new modules settling in around the DDR2-667 and DDR2-800 levels or above as we recently witnessed in our DDR2-1000 article -http://www.anandtech.com/memory/showdoc.aspx?i=273...">DDR2-1000 goes Higher.....
    Reply
  • AnandThenMan - Friday, April 14, 2006 - link

    quote:

    This may change in the future, but for now the move to AM2 and DDR2 memory looks like it will yield far too little in performance improvements to keep AMD competitive in the upcoming marketplace.


    It will be interesting to come back to this statement after AM2 and Conroe are out in the wild to see how accurate it was.

    Interesting article, but nothing very surprising to me. The Athlon64 core is pretty much at its computational limit at a given clock, feeding it with more memory bandwidth does little. Which means that early adopters of the AM2 platform will get 939 performance with an updgrade path, which is not too shabby.

    Conroe better live up to expectations though...
    Reply
  • Wesley Fink - Saturday, April 15, 2006 - link

    It would be a very pleasant surprise if AMD has us all in the dark and launches a Conroe competitive part or a Conroe-killer. Competition is good for buyers, especially when performance is very close. The close performance results in lower prices, as we are now seeing in the ATI/nVidia video cards from the most recent generation.

    However, we have to evaluate things with the best information we have available on time to Fab, launch dates, and the available revs that have been provided to AMD partners to design their companion products for the AM2 launch. There is always room for an unexpected surprise, but it looks less likely the closer we get to 6/6/06.
    Reply
  • Viditor - Saturday, April 15, 2006 - link

    I have no doubt that AM2 is a very weak upgrade...management at AMD said as much in their recent conference call.
    The only critique I have would be of the line
    quote:

    the move to AM2 and DDR2 memory looks like it will yield far too little in performance improvements to keep AMD competitive in the upcoming marketplace

    You should have added the word "desktop" before marketplace as the server marketplace should still be solidly AMD, and we have yet to see what will happen in the mobile space...JMHO
    Reply
  • Wesley Fink - Saturday, April 15, 2006 - link

    A very fair comment. I added the "desktop" qualifier since it makes sense. Reply

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